Strapping machine with short feed lockout

ABSTRACT

This machine straps a package with flexible tape strapping. A strap is initially fed by feed and tension wheels around the yoke and against a stop with which a gripper clamps the free end of the strap against an anvil, the feed is reversed to remove a slack loop in the strap at the feed mechanism and the feed mechanism is automatically stopped. Thereafter, a tensioning valve is operated to reactivate the feed mechanism so as to slip the strap out of the yoke, tension the strap around the package and join the ends of the strap after tensioning. Occasionally the apparatus malfunctions to produce a short feed, wherein during the initial feeding operation, the strap does not reach the gripper so that even though the gripper closes against its anvil, when the feed mechanism is restarted to tension the strap, the strap is pulled out of the yoke, instead of being tensioned around the package and hence must be rethreaded. To prevent this, an air orifice is provided at the gripper anvil which orifice is not covered by the free end of the strap when the aforesaid short, feed malfunction occurred, and the gripper was closed and this short feed condition prevents restarting of the feed mechanism in the tensioning direction when the aforesaid valve is operated to initiate tensioning. Thus, the strap is not withdrawn from the yoke and after the obstruction is cleared the strap need not be re-threaded through the machine.

United States Patent Buck [ 1 STRAPPING MACHINE WITH SHORT FEED LOCKOUT [75] Inventor: Erville C. Buck, Springfield, Oreg.

[73] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: Jan. 10, 1974 [21] Appl. No: 432,382

Primary Examiner-Billy J. Wilhite Attorney, Agent, or FirmC. E, Tripp 1571 ABSTRACT This machine straps a package with flexible tape strapping, A strap is initially fed by feed and tension wheels around the yoke and against a stop with which a gripper clamps the free end of the strap against an anvil, the feed is reversed to remove a slack loop in the strap at the feed mechanism and the feed mechanism is automatically stopped. Thereafter, a tensioning valve is operated to reactivate the feed mechanism so as to slip the strap out of the yoke, tension the strap around the package and join the ends of the strap after tensioning. Occasionally the apparatus malfunctions to produce a short feed, wherein during the initial feeding operation, the strap does not reach the gripper so that even though the gripper closes against its anvil, when the feed mechanism is restarted to tension the strap, the strap is pulled out of the yoke, instead of being tensioned around the package and hence must be rethreaded, To prevent this, an air orifice is pro vided at the gripper anvil which orifice is not covered by the free end of the strap when the aforesaid short, feed malfunction occurred, and the gripper was closed and this short feed condition prevents restarting of the feed mechanism in the tensioning direction when the aforesaid valve is operated to initiate ten sioning. Thus, the strap is not withdrawn from the yoke and after the obstruction is cleared the strap need not he re-threaded through the machine.

3 Claims, 29 Drawing Figures ON-OFF VALVE l 22 FOOT VALVE, V

U.S. Patent Oct. 21, 1975 Sheet1of18 3,913,472

FOOT VALVE,

FII3 l MOTOR, M

US. Patent Oct. 21, 1975 Sheet 2 of 18 PL ATENZG U.S. Patent Oct. 21, 1975 Sheet30f 18 3,913,472

wmzoazni U mH-H-P -U U.S. Patent 00.21, 1975 Sheet6of18 3,913,472

Sheet 7 0f 18 m M 0 @M 4 R Em P w R G REAR FRONT GRIPPERBZ;

ANVIL ORIFIGE, \03

F I I3 EEI FOOT VALVE TFV STRAP LIMIT /VALVE,SV

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ON- OFF VALV E 2.2.

NEEDLE VALVE,NV

FLAG,'1O

US. Patent Oct. 21, 1975 iTENSlON WHEEL36 TENSION LIMIT VALVE TV U.S. Patent Oct.21, 1975 Sheet80f18 3,913,472

FII3-EIA ANVIL ORIFIGEJOB (SEE FIG. l4)

3 NEEDLE VALVE,NV H

FLAG, '10

S '17. sv-z 10o. STRAP LIMIT 5 0 AS /vA| vE sv E REAR FRONT GRIPPERBZ RIPPERBO ON-OFF vALvEzz v-l I64 MOI/QR TENSION wl-lEEL se AS 2. FEED 1 P4 HA LINEAR ACTUATOR, \02. PE. MU.

CAMS I00 SOL. H F EXH IgV-G a I 3 L H r t- -r CAM 3 P I' As v LIMIT v-4 v A VALVE AS 4 g F2 4 OPEN 1 TENSION LIMIT A -6O VALVE,TV 1 G4 '1 7 U "(Kili I A U.S. Patent 0a. 21, 1975 Sheet 9 of 18 3,913,472

ANVIL ORIFICEJOB (BLOCKED) FOOT (SEE FIGS. IS a Is) VALVE FV AS SV-\ 4? O NEEDLE VALVE,NV phi-g v-a I TENSION WHEEL ,ae ELP V p FLAG/l0 q H As Ev.

5V 2. STRAP LIMIT 5 AS VALVE,

I .4 r-SV I OPENS REAR FRONT REVERSE g GRIPPERBZ GRIPPERBO M SHIFTS CLOSED ON-OFF v P' FN-WW2 2 r :1 LINEAR EXH' I t1!- AGTUATORJOZ -I A p- CAMS I SOL EX \00 IF H II V@ CM -1 EXH.

1 P CAM V ll V F" LIMIT 3 v-4 As v VALVE/1L r, r- AS I 2 I v-z A5 P 2 PEZ CLOSED vALvE -v W US. Patent Oct. 21, 1975 FIE IE ANVIL ORIHGE, (BLOCKED) FOOT VALVE OPENED Sheet 11 of 18 (SEE FIG. 2|)

TENSIONING TENSlON TENSION WHEELBE: SHIFTS 3.\ FLAG,"IO l 6 1 P53). V p

w v H ,-V5

12 ,g H STRAP um'r AS SHIFTS AS 7 VALVE,SV 2

H3 REAR 32 FRONT GRIPPER GRIPPERBO 0N OFF p1 -73? L '64 SEVAW ZZE 2 mm 3\ EXH.

PE-i V 1 LINEAR 4 ACTUATORJOZ. A P- SOL. 1 l l v-c Lu 1 l 5 v I As 4 l H H AS 2 v-z H p-Z. T'- fiPE-Z A 2 TENSION LIMIT -60 I l VALVEJV Ii 64 r 1' I US. Patent 0a. 21, 1975 Sheet 12 of 18 3,913,472

ANVIL ORIFIGEJOB (sEE FIG. 22) FOOT VALVE A5 FV s 2 35 O V! NEEDLE VALVE,NV V (GLOZED) CLOSED 1-.

EXH. TENSION WHEELBQ I;

FLAG,1O T CLOSED 1 tru: V-5

AS H STRAP umr A5 E g H TENSIONING REAR 32 FRONT STOPS GRIPPER GRIPPERBO ON-OFF VALVEZZ \64 CLOSED AW A 2 640.

d A P4 100 SOL. W 1; FL EXH.

II V P fC-LOSED ll L, P

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Ii p-Z A A5 TENsloN LIMIT l VALVE,TV"TA US. Patent 0m. 21, 1975 Sheet 13 of 18 3,913,472

' (SEE FIG. 9)

1 1 FIE 141 l FEEDING SV- CLOSED I FII3 lEi L (SEE FIG. l0)

S1;OP FEED OVER TRAVEL l8) STOF;,\9 24 O3 v n/BLOGKED 30 REVERSE STRAP LIMIT VALVE V JIIIIIIIIIK\\4 5 sv OPEN CLOSED 2.1

U.S. Patent Oct. 21, 1975 Sheet 14 of 18 3,913,472

(SEE FIG. IO)

STRAP LIMIT VALVE sv OPEN WITHDRAWS 21 30,CLOSED iLooP '5 ,OPEN Fl 1:3

STOPPED FIB EIII (SEE FIG. II)

sv, CLOSED U.S. Patent Oct.21, 1975 Sheet 15 0f18 3,913,472

32 OPEN (SEE FIG. l2)

TIGHTENED 32 STARTS CLOSING TIIEI' EE (SEE FIG. l3)

' TENSION LIMIT VALVE,T

STOPS MOTOR ,STARTS CAM \OO US. Patent 0ct.21, 1975 Sheet 16 of 18 3,913,472

FIB 3:EI

ANVIL ORIFIGE 103 (SEE FIG. 25)

% FOOT VALVE A5 OBSTRUCTION 36 NEEDLE VALVE, NV STOPPED TENSION WHEEL '56 FLAG,1O

D O STRAP LIMiT A5 TvALvE sv RE-GLOSES REAR EXH. GRIPPER PZ A5 ON-OFF V 1640.

2 H VALVE H PE-l LINEAR ACTUATOR, 102. J A P 100 I SOL CAMS F I V16 car. J l CL d P v V CAM 2 v4 As LIMIT tu ll VALVE z g a v-2. ll AS 3 pa T 4 1 PE-Z I H E N |oN A P .-;eo I I I 1 62 VALVE,TV vvv 1 US Patent 0x21, 1975 Sheet 17 of 18 3,913,472

FII3 E 1 ANvaL 0RiFiGE,\O3

I /(0PEN) (SEE FIG. 25)

FOOT VALVE FwE-FV v OPENED g NEEDLE VALVE,NV

TENSION WHEELBG FLAG,"lO

17. \sTRAP LIMIT AS H VALVE,SV

EXH. GA

M ON-OFF p A SNVALV ZZ z V PE-\ LINEAR 4 ACTUATOR, \02 F" A P CAMS K400 m u I V6- H i P I l (H1 "1. 2 V I E V P CAM V-4 l A5 %74 LIMIT g u. I ,---I- VALVE 4 I A3 g US. Patent Oct. 21, 1975 Sheet 18 of 18 3,913,472

TIG 2 El SEE FIG. 23)

I g; DESTRUCTION is 24 10a CLOSED L/LBEO.

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TII3 EE OPEN STRAPPING MACHINE WITH SHORT FEED LOCKOUT FIELD OF THE INVENTION This invention relates to apparatus for strapping articles such as packages and more particularly to improvement in such apparatus which eliminates the need for rethreading the machine in case the strap is not fed completely before the strap tensioning cycle is initiated.

DESCRIPTION OF PRIOR ART The apparatus of the present invention is an improvement over the US. Patent to Goodley No., 3,759,169, issued Sept. 18, 1973, and assigned to the FMC Corporation. Although the short feed sensing and lockout device of the present invention can be applied to other strapping machines, a brief explanation of the invention will be provided as it is applied to the machine of the aforesaid Goodley patent.

SUMMARY OF THE INVENTION A strapping machine to which the present invention is applied is described in detail in the aforesaid Goodley patent and enough of this exemplary machine will be referred to in order to provide a complete understanding of the invention in a detailed description that follows.

Briefly, in the aforesaid strapping machine the strap is fed by cooperating feed and tension wheels (driven by a reversible air motor) between a rear gripper and an anvil, through a yoke between a front gripper and the anvil and up against a stop at the anvil. This feed is initiated by the operation of an on-off valve. When the strap engages the aforesaid stop, a loop of excess strap develops at the feed mechanism which loop is sensed and causes the front gripper to clamp the strap end against the anvil as well as automatic initial reversal of the feed mechanism (in the tensioning direction) to remove the loop and upon removal of the loop, the initial reverse operation of the feed mechanism automatically stops. Now, if a package is in place within the yoke, a second or tensioning valve is operated (manually in the example given) which causes the feed mechanism to restart in the tensioning direction, pulling the strap clear of the yoke and tight around the package. Since the free end of the strap has been gripped by the front gripper against the anvil this prevents the strap from simply sliding out through the yoke during tensioning. With the free end of the'strap thus held, the tensioning operation causes the strap to be pulled radially free of clips in the yoke and to be wrapped around and tensioned on the package, whereupon the second gripper clamps the running end of the strap against the anvil and the two ends of the strap are joined (as by heat sealing) to hold the strap in tension on the package.

Occasionally a malfunction, termed a "short feed", occurs in that during the initial feeding operation initiated by the aforesaid on-off valve, the free end of the strap may strike an obstruction (such as foreign matter within the yoke) before the end of the strap passes between the front gripper and the anvil and engages the stop. Excessive curl of the strap may also give the effect of an "obstruction. When this short feed condition occurred, the prior machine was unable to discriminate between the obstructed condition and the normal condition wherein the strap end has passed between the front gripper and the anvil and against the stop. Since a loop will develop at the feeding mechanism whether the strap encounters an obstruction in the yoke, or reaches the stop as in normal operation, the feeding mechanism is stopped and initially reversed to remove the loop, whereupon it stops again. However, under a short feed condition, if the second or tensioning valve (which is a foot operated valve in the illustrated embodiment) is now depressed to restart the feeding mechanism in the reverse or tensioning direction, since the free end of the strap has not been gripped between the front gripper and the anvil, the strap will be pulled back through the yoke and if this pseudo-tensioning action is not stopped soon enough, the strap will be pulled through and out of the feeding mechanism itself. Thus in the prior machine, the first indication that an operator had that the device was not feeding properly was that the strap pulled through the yoke and feed mechanism during what should have been a tensioning operation. Thus in addition to finding the original cause of the malfunction during the feeding operation, the operator must rethread the machine, that is, the strap must be reintroduced into the feed mechanism and through the gripper and anvil structure before normal operation can be resumed.

In accordance with the present invention, the initial feeding of the strap, stopping the feed, and initially reversing the feed to remove the loop at the feeding mechanism takes place as before, upon depressing of the on-off valve. However, when the aforesaid tensioning valve which is provided to initiate the final tensioning operation is depressed, the present invention disables or locks out the feed and tensioning mechanism so that the latter cannot be restarted in the tensioning direction and hence will not pull the strap clear of the mechanism. The preferred method of attaining the aforesaid feature and advantage of the present invention involves a simple addition to an air valve pilot circuit that controls the reversible air motor for the feed mechanism. Briefly, when the tensioning valve is operated to initiate the final strap tensioning mechanism after strap feeding has been completed, a pilotoperated valve is shifted which directs air to the air motor (under normal conditions) to initiate the tensioning operation. Under the present invention, the anvil for the front gripper that normally grips the free end of the strap is provided with an air orifice and when the strap is fed between the front gripper and the anvil and the front gripper closes, this anvil orifice is blocked or closed off by the end of the strap and final tensioning will take place upon operation of the aforesaid tensioning valve. However, when the strap end does not reach the aforesaid front gripper and anvil, even though that gripper is closed as usual, since the gripper has a serrated jaw, the aforesaid orifice in the anvil is not blocked and hence air will escape from the anvil orifice when the aforesaid tensioning valve is operated to initiate final tensioning. This escape of air from the anvil orifice bypasses a sufficient amount of air from the aforesaid pilot operated valve that is provided to reverse the feed motor and initiate tensioning so that the valve pilot does not shift the pilot operated valve, as in normal operation. Under this short feed condition, even though the manually operated tensioning valve is operated to initiate tensioning, the motor which drives the feed and tensioning wheels does not restart in the 

1. Article strapping apparatus of the type comprising a reversible motor driving strap transport wheel means in one direction for feeding a strap through an article receiving yoke and between an anvil and gripper assembly to bring the end of the strap against a stop, means for thereupon closing the gripper to clamp the eNd of the strap against the anvil, and control means for reversing the motor to cause the transport wheel means to slip the strap free of said yoke and tension the strap about an article within the yoke; the improvement comprising an air orifice in said anvil and gripper assembly which orifice is blocked only when the strap end passes between said anvil and gripper assembly and the gripper closes, said control means comprising a source of air under pressure, a tensioning initiating valve between said source and said orifice, and means for preventing reverse motion of said motor and said transport wheel means sufficient to withdraw the strap from said yoke when said tension initiating valve is opened and said orifice is open due to failure of the end of the strap to reach said gripper during said strap feeding operation.
 2. The apparatus of claim 1, wherein said air orifice is in said anvil and opens toward said gripper, and said gripper has a corrugated jaw that permits escape of air from said orifice when no strap end is present.
 3. The apparatus of claim 2, whereby said control means includes a pilot operated valve having a pilot connected in a line from said tension initiating valve for reversing said motor, said orifice being connected to bleed air from said line and an adjustable needle valve in said line between said tension initiating valve and said valve pilot. 